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Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A2961F000C4; Sat, 14 Nov 2026 11:48:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794656933; bh=ffBvyljZwir56F/o+pX+z6WA5o/3P/Rv7qQXfu5q+ms=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=ecu0Cg2ydLJNywqcQhRPjlnB40j5NeGKQ9VNL1F8kEZFKiXUtCAXQGGbnNcEX3ZG6 8+CGfQlW44Kzg3dRkViDeEbtFbA+/ftciETZSczaTUFrgj9on5U7wT1hyJeeTp/vWO np2lWLBh4vX9pi14FkLoO6RhtZ1Ga9VQeNIVNsugtaZdgbt733hj6CJ2yh8s2ZAors LqjPkzRumRgzhCS8GUxEC1lntZTgZlNqQcIdKlaDLczRtmhg1+RR2VXeORTfb64YKj RllChRKY8EXylk6wmxkycSd8B3tUwzNpVYXnQmcO6JJaEC/FwrK9bTs9vDrnEUKh20 h13rzWPGC/mIQ== Message-ID: <41522fcf40be21bb11409189204bb62ffac47ae4.camel@kernel.org> Subject: Re: nfsd: delegated timestamps get written to frozen filesystems From: Jeff Layton To: Christian Brauner , Chuck Lever Cc: NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , Jan Kara , linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Sat, 14 Nov 2026 06:48:50 -0500 In-Reply-To: <20261114-abdrehen-mahnwache-farbpalette-9c31774145cc@brauner> References: <20261114-abdrehen-mahnwache-farbpalette-9c31774145cc@brauner> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf CBYyUE8QJpvTZyfUHNYldXlrjO6n5MdOempLqWpfOmcGkwnyNRBR46g/jf8KnPRwXs509yAqDB6sE 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AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.62.1 (3.62.1-1.fc45) X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Sat, 2026-11-14 at 10:35 +0100, Christian Brauner wrote: > Hey, >=20 > I'm working on a freeze protection series. This fell out of it and I > can't just fix it myself. >=20 > Can I leave you with fixing this? >=20 Yes. I'm currently working on a patchset to rework how delegated timestamps are handled. I'll plan to roll some freeze protection into the series (or in a trailing one if that's more suitable). No promises on the timeframe though. Cheers! Jeff > cb_getattr_update_times() and nfsd_update_cmtime_attr() call > notify_change() under inode_lock() but nothing takes freeze protection > for the export. So they modify filesystems that are frozen. On ext4 that > trips the WARN_ON() in ext4_journal_check_start(). >=20 > Reproduced on v7.4-rc1 with two NFSv4.2 clients, the second one in its > own network namespace: >=20 > - client A opens a file O_RDWR and gets a write delegation > - the export gets frozen > - client A writes 64k into the file and keeps it open, so the data > stays in its page cache > - client B runs stat on the file >=20 > nfsd sends CB_GETATTR to client A, sees the file was modified and > updates the timestamps on the frozen filesystem: >=20 > WARNING: fs/ext4/ext4_jbd2.c:90 at ext4_journal_check_start+0x1f6/0x2d0= , CPU#0: nfsd/444 > Call Trace: > __ext4_journal_start_sb+0x7a/0x470 > ext4_dirty_inode+0xa1/0x120 > __mark_inode_dirty+0x154/0x1110 > ext4_setattr+0x2bd/0x24e0 > notify_change+0x81c/0xee0 > nfsd4_deleg_getattr_conflict+0x7f0/0x1370 > nfsd4_encode_fattr4+0x3c3/0x1290 > nfsd4_encode_getattr+0xd1/0x1d0 > nfsd4_encode_operation+0x285/0xf80 > nfsd4_proc_compound+0x5e2/0x23c0 > nfsd_dispatch+0x26d/0x870 > svc_process_common+0xfed/0x19a0 > svc_process+0x600/0xb90 > svc_recv+0x1969/0x2650 > nfsd+0x2f8/0xcd0 >=20 > The inode's mtime and ctime on the server change while it is frozen. > That was with delegated timestamps turned off, the > cb_getattr_update_times() path with them on is the same. >=20 > I think nfsd_update_cmtime_attr() has the same problem > but I haven't reproduced that variant. It runs from: >=20 > - nfsd4_copy(), nfsd4_do_async_copy(), nfsd4_clone() > - nfsd4_finalize_deleg_timestamps() <- nfs4_unlock_deleg_lease() <- > destroy_unhashed_deleg(), which is reached from DELEGRETURN, > nfs4_open_delegation(), the laundromat via revoke_delegation(), admin > revocation, client teardown and nfs4_state_shutdown_net() >=20 > mnt_want_write_file() on the delegation's file before inode_lock() would > do for GETATTR, COPY, CLONE and DELEGRETURN. >=20 > But the laundromat and nfs4_state_shutdown_net() shouldn't block on a > frozen export, I think? Lease expiry for the whole net would stall and > nfsd shutdown would hang until the thaw. Those probably want > sb_start_write_trylock() and skip the timestamp update while frozen. >=20 > The OPEN with truncate path in nfsd4_truncate() had the same problem. > I've got a fix for that one in my series. >=20 > This goes back to 7e8ae8486e44 ("fs/nfsd: fix update of inode attrs in > CB_GETATTR") and e5e9b24ab8fa ("nfsd: freeze c/mtime updates with > outstanding WRITE_ATTRS delegation"). --=20 Jeff Layton